1. Field of the Invention
This invention relates to electronic control of an axle assembly for use with a vehicle drive train, for example, a torque-coupling device; and more particularly is directed an electronically controlled actuator directly connected to the differential case to control a clutch in such an axle assembly.
2. Background of Related Art
Limited slip differentials, or torque coupling devices are well known in the art. In such limited slip devices, a hydraulically actuated friction clutch pack is actuated to retard relative rotation of at least one of the output shafts relative to the differential case. Normally, hydraulic pressure is directly increased in response to an increase in rotational speed differential of the output shafts or when a specific output shaft exceeds a predetermined limit. One common way to provide the hydraulic pressure is to include an internal pump, or gerotor pump, within the differential case which increases a clutch action on one shaft as the rotational speed increases. However, these prior art devices do not provide the ability to selectively control the pressure in the clutch pack and consequently the amount of limited slip or selective torque transfer. Other devices provide a controlled pump external to the differential housing and required complicated and costly hydraulic rotatable interfaces between the housing and differential case. An object of the present invention is to overcome the drawbacks of the prior art devices.
The present invention provides electronic control of a differential assembly. An electronically controlled solenoid valve is formed on the external surface of the differential case and is connected to a passageway leading to a clutch pack within the differential case to establish fluid communication there between. The clutch pack is arranged to selectively couple one of the output shafts with either the differential case or the other output shaft. A pump is provided within the differential case to force the clutch to couple the output shaft as previously noted. The solenoid valve is electronically controlled to selectively relieve pressure within the differential case and clutch assembly to selectively control coupling of the output shaft.
The objects, features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.